1. Field of the Invention.
The present invention relates to a method of treating water polluted by organic chlorine compounds.
2. Description of the Prior Art
Recently, water in river and underground water have been polluted by various kinds of harmful substances and therefore, they are not suitable for drink or for industrial use unless they are treated. It is a matter of common knowledge that this is a serious social problem.
The main cause, of polluting water in river and underground water is industrial drainage and wastewater to river. In addition to this industrial drainage, there is a case such that unexpected drainage and wastewater become a cause of polluting water in river and underground water. For example, a treatment solution used in dry cleaning contains tetrachloroethylene. When a waste liquid of dry cleaning is discharged into rivers without treatment, this becomes also a major cause of polluting water in water and underground river.
As technologies of treating tetrachloroethylene contained in a waste liquid, there has been conventionally known an adsorption method using activated carbon, an adsorption method using high molecular adsorption agent and a reduction treatment method using metallic irons. Among these methods, the adsorption method using activated carbon is an effective treatment method and it has been now employed.
However, in waste liquids, including industrial drainage and a waste liquid produced by the dry cleaning procedure and containing organic chlorine compounds such as tetrachloroethylene, other components used for the treatment, e.g., a surfactant, dirt or soil generated by the treatment, dyestuffs as well as components such as humic acids, fluvie acids, alcohols, ketones, etc. are contained together. Thus, when the activated carbon-adsorption method is used, the activated carbon is saturated immediately after the start of adsorption by the above-mentioned components, so that an effective treatment of organic chlorine compounds is not made.
In order to solve this problem, it was developed an ultraviolet-ray decomposition treatment, in which an oxidizing agent such as ozone, etc. is added in exhaust water and an ultra violet rays are irradiated to oxidation-decompose organic chlorine compounds. (Japanese Patent Application Laid-open No. Hei 4-7082)
Also, in U.S. Pat. No. 5,234,606, organic chlorine compounds are oxidation-decomposed by irradiation of ultraviolet rays onto oxidizing agent added before and remaining in water to be treated.
However, in the method according to the prior art, the treatment ability is affected by the permeating degree of ultraviolet rays into the waste liquid. When the waste liquid is made turbid by dyes, it is difficult to treat the waste liquid. Even though water to be treated is clear, when water contains an organic component such as a surfactant, the oxidation-decomposition of the organic chlorine compound of itself is inhibited and thus, sufficient treatment can not be conducted.